1. Field of the Invention
The present invention concerns a method for soldering lead-out wires to electronic components. It also concerns a component fitted with at least one external connection by metal wire soldered by the method of the invention.
2. Description of the Prior Art
Many components have their external connections made by means of metal wires, generally of copper, with a diameter of about 0.6 to 0.8 mm. These wires are used, firstly, to handle the component, and then, secondly, to fix it to a substrate or circuit. These functions are secondary with respect to the main function which is to provide electrical access to the component.
The fixing of these wires has to be mechanically strong, and must possess low electrical resistance and be convenient for the assembling method and economical at the same time.
Among known methods, the following are essentially used on an industrial scale:
dip soldering, in still baths or by wave soldering,
reflow soldering either with a solder paste or with a surplus of tinning given to the connection wires.
Dip soldering does not give excellent industrial scale results because the component, subjected to an Archimedean thrust, when it is dipped in the molten solder bath, gets moved with respect to its connection wires.
Soldering with solder paste is costly. Finally, reflow soldering by reflow of surplus tinning on the wires is imprecise: when the tinning of the wires melts, the component is not properly held in place since there is a liquid film between the component and the connection wire.
The invention enables the elimination of these drawbacks and facilitates the soldering of the wires to a component with perfectly localized soldering, at low cost, and gives a well-positioned component. The method according to the invention consists in providing the end of a connection wire, to be soldered on a component, with a solder preform. This preform does not completely surround the lead-out wire so that this wire can be in direct contact with the component on which it leans. The wire is deformed locally beforehand, to remove its axis of symmetry and prevent the rotation of the solder preform around the wire. The solder on the component of the wire thus coated is done by reflow process.